1. Field of the Invention
The present invention relates to seed meters for metering individual seeds at a controlled rate into a seed furrow, and more particularly to a seed meter seed disk which can be advantageously used with sunflower seeds and other seeds of long, slender shape and low mass.
2. History of the Prior Art
Seed meters of various designs have been employed to dispense seeds at a controlled rate into a seed furrow as the seed meter is advanced along the furrow. In a typical arrangement a tractor is coupled to tow a tool bar to which are attached in generally parallel, spaced-apart relation a plurality of planting units with seed meter arrangements attached thereto. Each of the planting units includes a seed hopper for containing a quantity of the seed to be planted, a device for opening a furrow as the tractor drawn tool bar is advanced over the ground, a seed meter coupled to the seed hopper for metering or dispensing individual seeds into the furrow at a controlled rate and a further device for moving soil at the sides of the furrow to close the furrow over the seeds. The planting unit may further include containers for insecticide and herbicide together with apparatus for dispensing controlled amounts of each.
Many seed meters are of the air type which use an air pressure differential to pick up and then discharge individual seeds from a seed mass in controlled fashion. Typically, a rotating seed disk having one or more circumferential rows of apertures therein is used to pick up and then discharge the individual seeds.
Air seed meters may be of the positive pressure type in which air is blown into a seed chamber and onto the surface of the rotating seed disk or other movable member to create a higher than atmospheric pressure in the chamber. This forces seeds from a seed mass onto the seed disk where they are retained in the apertures for later release. The seeds are held against the apertures by blowing air until they are released by interrupting the flow of air to the seeds. Examples of such air seed meters are provided by U.S. Pat. Nos. 3,888,387 of Deckler, 4,047,638 of Harrer and 4,074,830 of Adams.
Air seed meters may also be of the vacuum type in which a vacuum source is typically coupled to a separate chamber on the opposite side of the seed disk from the seed mass. The vacuum communicates through apertures in the seed disk to the seed mass to hold the seeds in place against the apertures as they are picked up from the seed mass and moved to the seed discharge area. An example of a vacuum seed meter is provided by U.S. Pat. No. 3,608,787 of Grataloup.
A further example of a vacuum seed meter which has particular advantages over seed meters of the prior art is provided by a co-pending application of William R. Lundie et al, Ser. No. 546,834, filed Oct. 31, 1983 and commonly assigned with the present application. The Lundie et al application describes a vacuum seed meter in which a seed disk is rotatably mounted within a housing so as to divide the interior of the housing into a first chamber adjacent a first side of the seed disk and an opposite second chamber at the opposite or second side of the seed disk. The seed disk is provided with one or more circumferential rows of apertures which extend through the thickness of the seed disk from the second side of the disk and terminate at the bottoms of recesses in the first side of the disk which define seed cells. The seed cells act to agitate, accelerate and then capture therein individual seeds from a seed mass within the first chamber. The individual seeds are held within the seed cells by a vacuum source coupled to the second chamber as the seeds are transported from the seed mass to a separate seed discharge area within the first chamber. At the seed discharge area the vacuum source is cut off from the apertures in the seed disk, allowing the individual seeds to fall out of the seed cells and through a chute to the ground below. The vacuum seed meter is usable with various different types of seeds, simply by changing the seed disk. Different seed disks have different sized apertures and different sizes and configurations of the connecting seed cells depending on the particular seed or type of seed to be metered by the seed meter.
Seed disks of the type shown and described in the previously referred to co-pending application Ser. No. 546,834 of Lundie et al have been found to work very well with most types of seeds. The recesses in the disk surface which form the individual seed cells typically provide adequate seed agitation and acceleration within the seed mass such that an individual seed is picked up and retained within each seed cell. Separate fins can be provided on the side surface of the seed disk where necessary to provide additional seed agitation. The seed cells are sized and configured to receive and retain a single seed therein, while additional seeds are caused to fall away from the seed cell and back into the seed mass. The vacuum source communicates with the individual seed within each seed cell through the aperture at the bottom of the cell recess to assist in holding the seed in place until the seed discharge area is reached.
However, certain difficulties occur when seed disks of this type are used with sunflower seeds and other seeds having a long, slender shape and relatively low mass. Because of the relatively low mass, the aperture extending through the seed disk from the bottom of the recess must be relatively small so as to minimize the amount of force communicated to the seed cell by the vacuum source. With the larger apertures used with most seeds, the much stronger force from the vacuum source tends to hold two or more seeds within or in the region of each seed cell rather than the desired single seed, due to the relatively low mass of such seeds. The reduced force which results from a smaller aperture is adequate to hold a single sunflower seed or similar seed within a seed cell after the seed has become seated within the cell. However, due to the long, slender shape of such seeds and the considerably reduced vacuum force, it is difficult to reliably pick up such seeds in seed cells comprised only of a recess within the disk surface, even where fins are provided on the side surface of the disk to increase seed agitation. The long, slender seeds assume a variety of different positions within the recesses, from which it is very easy for the seeds to slip or tumble out of the seed cell recess in the face of the reduced force from the vacuum source provided by the smaller aperture.
Accordingly, it would be desirable to provide an improved seed disk for use with seeds such as sunflower seeds which have a relatively long, slender shape and a relatively low mass.